What is the value of y?
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26.8% of examinees will score between 600 and 700.
This question is based on z score concept.
A Z-score is a numerical measurement that describes a value's relationship to the mean of a group of values. Z-score is measured in terms of standard deviations from the mean. If a Z-score is 0, it indicates that the data point's score is identical to the mean score.
where:
μ is the mean
σ is the standard deviation of the population
Given:
μ = 560
σ = 90
For
600≤ X≤700
for x = 700
Z score =x - μ/σ
=(700 - 560)/90
= 1.55556
P-value from Z-Table:
P(560<x<700) = P(x<700) - 0.5 = 0.44009
for x = 600
Z score =x - μ/σ
=(600 - 560)/90
= 0.44444
P-value from Z-Table:
P(560<x<600) = P(x<600) - 0.5 = 0.17164
∴ P(600<x<700) = P(560<x<700) - P(560<x<600)
= 0.44009 - 0.17164
=0.26845
∴26.8% percentage of examinees will score between 600 and 700.
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